It is known in the case of internal combustion engines that only 40% of the energy stored in the fuel is used to move the piston and thus to drive the internal combustion engine. The remaining energy generated in the context of the combustion is predominantly discharged from the internal combustion engine in the form of heat through escaping combustion exhaust gases. To reduce such heat losses and thus also to increase the efficiency of the internal combustion engine, it is known to couple an axial piston machine to the internal combustion engine.
For example a generic axial piston machine with a shaft, which is coupled to a swash plate in a rotationally fixed manner, is known from DE 10 2011 118 622 A1. A plurality of cylinders, in which pistons are in each case arranged so that they can be moved translationally, are thereby arranged coaxially to the shaft and in an annular manner around the latter. Each of these pistons is coupled to the swash plate via a corresponding spherical bearing and a sliding block, whereby a movement of the respective piston effects a drive of the swash plate and thus a driving of the shaft. Each inlet opening of a cylinder is thereby swept once in response to each rotation via a control plate comprising an eccentrically arranged passage opening, and working medium is thereby supplied to the respective cylinder. Provision is made in the central area of the axial piston machine around the shaft for a cavity, which is defined by the control plate, wherein the outlet openings, which belong to the cylinders, are guided through the cylinder head in such a way that a temporary connection between the cavity and the expansion volume of the cylinder can be established via the off-axis passage opening of the circumferential control plate. In particular the efficiency is to be capable of being increased through this.
In general, axial piston machines, in which a compressed medium, which is evaporated by exhaust gas, expands and thus creates mechanical energy, are used in heat recovery systems. In order to thereby be able to attain the highest possible efficiency, it must be ensured that only one of the cylinders is in fact filled, while the other inlet openings of the remaining cylinders are closed in an absolutely tight manner. Due to the fact that a rotating valve plate, which has a valve opening, is typically used as inlet control valve, a sealing must thus take place at a circumference of this valve plate. The sealing hereby typically takes place via so-called slightly raised “sealing eyes”, which surround the inlet openings in an annular manner and are thus also called sealing rings.
Due to the fact that an axial piston machine represents a thermally highly-stressed system and due to the fact that a housing thereof as well as a cylinder head can heat up to varying extents during operation, different axial expansions can occur, which, in the extreme case, leads to a bulging of the cylinder head and, associated therewith, to a lifting of the valve plate off the sealing eyes, thus resulting in leakages, which reduce the efficiency.
The invention at hand thus deals with the problem of specifying an improved or at least an alternative embodiment, which has an increased efficiency in particular due to an improved seal, for an axial piston machine of the generic type.
According to the invention, this problem is solved by means of the subject matter of the independent claim(s). Advantageous embodiments are the subject matter of the dependent claims.